<PAGE>

THE SECURITIES EVIDENCED HEREBY HAVE NOT BEEN REGISTERED UNDER THE UNITED STATES
SECURITIES ACT OF 1933, AS AMENDED, (THE "SECURITIES ACT") AND MAY NOT BE SOLD,
TRANSFERRED, PLEDGED, ASSIGNED, HYPOTHECATED OR OTHERWISE DISPOSED OF EXCEPT IN
ACCORDANCE WITH THE TERMS OF AN AGREEMENT BETWEEN THE ISSUER AND THE ORIGINAL
UNDERSIGNED OF THE SECURITIES, A COPY OF WHICH IS ON FILE AT THE PRINCIPAL
EXECUTIVE OFFICE OF THE ISSUER.

                         AMENDMENT TO WARRANT AGREEMENT TO
                             PURCHASE COMMON SHARES OF

                               MYO DIAGNOSTICS, INC.

     This AMENDMENT TO WARRANT (this "Amendment") is made as of December 6,
1997, by and between Myo Diagnostics, Inc., a California corporation (the
"Company") and _________________________________ (the "Holder").

     A.   WHEREAS, __________________________________ (the "Holder") is the
holder of that certain Warrant dated December 6, 1996 for shares of the Common
Stock of the Company (the "Warrant"); and

     B.   WHEREAS, the Company and the Holder desire to amend the Warrant as
hereinafter provided

     NOW, THEREFORE, in consideration of the promises and for other good and
valuable consideration, the receipt of which is hereby acknowledged, the parties
hereto hereby agree as follows:

     1.   The introductory paragraph of the Warrant is hereby amended to read in
its entirety as follows:

     THIS CERTIFIES that, for value received, ______________ (the "Holder"), is
the registered holder of _______ warrants (the "Warrants").  Each Warrant
entitles the holder, subject to the terms and conditions set forth in this
Certificate, to purchase from Myo Diagnostics, Inc. (the "Company"), one fully
paid and non-assessable Common Share of the Company (the "Share") at any time
commencing on the date hereof and continuing up to 5:00 p.m. (Toronto time) on
December 31, 1998 (the "Time of Expiry") on payment of U.S. $3.00 per Share (the
"Exercise Price").  The number of Shares which the Holder is entitled to acquire
upon exercise of the Warrants and the Exercise Price are subject to adjustment
as hereinafter provided.


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     2.   The Company hereby represents and warrants to the Holder that this
Amendment has been duly executed and delivered by the Company and that the
Warrant, as amended by this Amendment constitutes the legal, valid, and binding
obligation of the Company, enforceable against the Company in accordance with
its terms.

     IN WITNESS WHEREOF the Company has caused this Certificate to be signed by
its duly authorized officers and its corporate seal hereto affixed.


 MYO DIAGNOSTICS, INC.


Dated: January ___, 1998


Signature:
          -------------------------

Print Name:    GERALD D. APPEL
           ------------------------

Its:   PRESIDENT
    -------------------------------


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                                    SCHEDULE "A"

                                ELECTION TO EXERCISE

     The undersigned hereby irrevocably elects to exercise the number of
     Warrants of Myo Diagnostics, Inc. set out below for the number of Shares as
     set forth below:


          (a)  Number of Warrants to be Exercised:               ____________

          (b)  Number of Shares to be Acquired:                  ____________

          (c)  Exercise Price per Share:                         ____________

          (d)  Aggregate Purchase Price [(a) multiplied by (c)]  ____________

     and hereby tenders a certified cheque, bank draft or cash in United States
     dollars for such aggregate purchase price, and directs such Shares to be
     registered and a certificate therefor to be issued as directed below.


          DATED this_____day of__________________, 199__


               ---------------------------------

               Name of Holder


               By:
                  ------------------------------